Switch Sports is doing well and should have good legs as most Nintendo ever greens do, but it doesn't seem like it will be a system selling phenomenon type of thing with Switch sales being down YoY by a pretty notable clip.
Wii Sports Resort had 349k opening week and a 153k second week and then a 99k third week, 70k fourth week, 69k fifth week according to this site in Japan, Wii Sports Resort didn't go below 50k until like it's 9th week in Japan. I would expect decent legs though as there's not much in the way of other huge Switch releases for a while.